fix(portal): screen-capture script, portal backend, swaync autostart

screen-capture.sh was a single non-executable line containing a `slur` typo,
so it never ran and nothing referenced it; rewritten as a working region
capture to ~/Pictures plus clipboard.

xdg-desktop-portal/portals.conf pins the wlr backend for sway, and swaync is
pulled in via graphical-session.target.wants so the portal's
Requisite=graphical-session.target is satisfied (the reason screen sharing
previously never started).

.config/xdg-desktop-portal/portals.conf

@@ -0,0 +1,22 @@
+# Portal implementation pinning for the SWAY session.
+#
+# Without this file xdg-desktop-portal fell back to the deprecated `UseIn` key
+# and picked hyprland.portal at random ("Choosing hyprland.portal ... via the
+# deprecated UseIn key"), while the sway config also started the wlr portal --
+# two implementations registered at once.
+#
+# Base is Arch's own /usr/share/xdg-desktop-portal/sway-portals.conf.
+# GlobalShortcuts is added because neither wlr nor gtk implements it, and
+# easyeffects requests it (journal: "Unknown method CreateSession or interface
+# org.freedesktop.impl.portal.GlobalShortcuts").
+
+[preferred]
+default=gtk
+org.freedesktop.impl.portal.ScreenCast=wlr
+org.freedesktop.impl.portal.Screenshot=wlr
+# gtk's Inhibit uses org.gnome.SessionManager / org.freedesktop.ScreenSaver,
+# neither of which sway implements; "none" lets apps use Wayland's
+# idle-inhibit protocol, which sway does implement.
+org.freedesktop.impl.portal.Inhibit=none
+org.freedesktop.impl.portal.GlobalShortcuts=hyprland
+org.freedesktop.impl.portal.InputCapture=hyprland